To date, temperature cycling tests have been conducted to analyze joint quality and reliability of electronic components which are soldered to printed wiring boards. During the temperature cycling tests, thermal stresses are induced on a solder joint by repeatedly changing the temperature. In the temperature cycling test, the quality and reliability of a solder joint may be estimated by checking whether any cracks have formed in the solder joint and/or by checking the depth, the growth, the location, etc. of the cracks. In a typical method of analyzing cracks, after the solder joint is cut perpendicular to the printed wiring board and then the cut surface is polished, the polished cut surface is observed by a Scanning Electron Microscope (SEM), for example.
However, according to the above-mentioned analyzing method, only cracks that appear on the cut surface may be observed. That is, for example, when a plurality of solder joints is provided over a single electronic component, it is desirable for a plurality of cut surfaces to be prepared. Thus, the amount of time and effort spent in cutting the solder joint and polishing the cut surface may be significant, and the operation efficiency may be poor. Furthermore, for example, in case of a crack spreading out parallel to the printed wiring board, it is difficult to observe the overall feature of the crack.
In Japanese Laid-Open Patent Publication No. 9-264854, a method of observing the torn surface of the solder joint by tearing off the solder joint along the expanded face of the crack is discussed.
However, it is difficult to maintain the original condition of a crack while tearing off the solder joint. For example, using a tensile strength testing device to pull off an electronic component from a printed wiring board may cause ductile fracture in the solder joints and deformation of the solder joints and cracks therein. Furthermore, deformation of the solder joints and cracks may cause additional scratches and cracks. As a result, it may be difficult to distinguish a crack caused by thermal stress from one caused by physical stress.
Thus, according to the above-mentioned analyzing method with a tensile strength testing device, enhancing the accuracy of analyzing the cut surface is difficult because tearing-off traces may be left over the cut surface.